Chiu, Ya-Chu (National Taiwan University) | Lee, Chia-Han (National Taipei University of Technology) | Liu, Hsiao-Hua (National Taipei University of Technology) | Wang, Tai-Tien (United Geotech, Inc.) | Huang, Tsan-Hwei (National Taipei University of Technology)
Deep-seated gravitational slope deformation (DGSD) is characterized by progressive movement on and beneath ground surface. Such large, slow and complex deformation is usually difficult to define. A tunnel crosses through a deep-seated creeping slope deforms with the slope, demonstrating lasting damages. The patterns and transformation of these damages vary from section to section. To decide a legitimate maintenance strategy, the deformation characteristics of each section in the tunnel should be clarified first.
The case tunnel is located on a deep-seated moving slope in southeastern Taiwan. From 1991, two years after the tunnel is built, until now, damages are continually reported. According to investigations of ground surface displacements, it is very likely that more than one boundaries of slope moving masses pass through the tunnel. Within the possible areas in the case tunnel influenced by the moving slope, this study set monitoring profiles every 5 m for 150 m long. About every half a year in 2009-2012, an integrated geodetic survey method having 3-5 mm accuracy – the micro-displacement monitoring technology is employed to measure the absolute three dimensional positions of the monitoring points. Consider each tunnel profile as a unit, the displacements of the monitoring points on a profile are decomposed into the rigid body motion and the deformation of the corresponding profile. The rigid body motions are further separated to in-plane and out-of-plane translation.
The exquisite geodetic survey results indicate that the amount of translation descended from the western portal to the east. At the two distinct locations where more than 150 mm dislocation can be visually identified (about 33 m and 100 m from the western portal), the translation has a considerable drop. Between August 2009 and April 2010 after the tremendous Typhoon Morakot, the displacements of every profile increased markedly, and decreased to the usual amount in the next half year. The tunnel is divided by six zones, three deformation zones, two seriously deformation zones and a transition zone based on the monitoring data.
The Kandri underground mine of MOIL Ltd in India at present is spread in four levels i.e. (-) 50’L, (-) 150’L, (-) 250’L and (-) 350’L, with 30 m vertical intervals. Total strike length of Kandri deposit is approx. 600 m, which is divided into North Limb, South Limb, South Limb Extremity. The wide thick ore body encountered in the South Extremity is of great importance to MOIL from recovery point of view. At the same time, method for its recovery is also challenge due to the complex rock mass and geological structure. Since, the orebody in this part is suddenly plunge to 25-30 degrees from the earlier 45-50 degrees. Moreover, the overlying strata are also saturated with water. In the present paper, rock mechanics studies carried out with empirical and numerical approaches applied to derive safe stoping parameters and support system will be presented. In view of the present infrastructure and trained manpower, Room-and-Pillar with post-pillar as a possible method of stoping operation is suggested and discussed herewith. The representative case study from a typical man-entry cut-and-fill stoping environment from the Kandri Mine in MOIL Ltd. is presented to demonstrate how hydraulic sand fill and left out pillars act as a good support measures.
The method of micro-macro decoupling analyses is applied to assess the macroscopically anisotropic strengths of alternate layers of inclined rock masses, which are characterized by the layered structure of sedimentary soft rocks, in consideration of yield and tensile/compressive strengths of rocks at micro-scale. To evaluate the macroscopic strength characteristics, a series of numerical material testing, which is based on the mathematical homogenization theory, is conducted on a unit cell composed of mudstone and sandstone, each of which exhibits consolidation-pressure dependent plastic deformations as well as tension-cut-off-type damage behavior. Numerical examples are presented to demonstrate the performance of the presented strength assessment scheme in view of design and analysis of important structures encountered in practical applications.
We investigated spatial and temporal the distribution of trace metals and sedimentary particles in order to identify the relationship between benthic foraminifera and trace metals pollution within Gunnamatta Bay, Port Hacking Estuary, NSW, Australia. Risk assessments of surface sediments were conducted using hierarchical cluster analysis (HCA).A total of 59 surface sediment samples and seven subsurface sediment samples were collected in order to determine the spatial and temporal distribution of trace metals in the bay. Further, six surface sediment samples were examined for existing foraminiferal assemblages. These included muddy samples which had high and low concentrations of trace metals and sandy samples. The trace metals distribution showed that chromium, nickel, copper, zinc, arsenic, lead, rubidium and bromine had similar distributions in surface sediments. The results of trace metal concentrations were also compared with the deleterious biological effect values in marine sediments. The means of most concentrations of trace metals for the Bay were below the Effect Range Median (ERM) or the Effect Range Low(ERL),except for copper. The highest concentrations of these metals were found to be in the north east of the bay, close to discharge points and a boat yard at GU55, with concentrations of 107, 14, 398, 413, 8, 203, 27 and 182ppm respectively. Also, this trace metal pollution was found to be concentrated in the inner part of the bay, which is deep and has organic matter and clay minerals. The benthic foraminiferal assemblages had lower species diversity in the muddy samples than in the fine sandy particle samples .Furthermore, the muddy particles that had high levels of trace metals were dominated by pollution-tolerant species such as Ammonia beccarii, Brizalina spathulata and Elphidium excavatum, which have had more opportunity to flourish. In addition, the levels of trace metals dramatically declined with increasing depth. This indicates that the potential source of trace metal pollution has been from human activity, such as boating and emission of gasoline fumes, since early European settlement in this area.
Elsworth, D. (Pennsylvania State University) | Gan, Q. (Pennsylvania State University) | Marone, C. (Pennsylvania State University) | Connolly, P. (Chevron Energy Technology Company) | Alpern, J. (Pennsylvania State University) | Culp, B. (Noble Energy) | Im, K. J. (Pennsylvania State University)
Gaseous stimulants offer some advantages in the “hydraulic” fracturing of low permeability reservoirs over traditional water-based fluids. These include conserving water as a resource, avoiding the activation of clays with added water, in potentially sequestering greenhouse gases and in utilizing competitive sorption for the improved recovery of the hydrocarbon reserve. In addition, the energetics of the gas stimulant may be advantageous in developing networks of increased complexity. Experimental observations are presented of the influence of gas composition and state on the breakdown pressures and evolving fracture complexity of fractures driven by gas – as an analog to hydraulic fracturing in situ for hydrocarbon recovery – for example in gas shales. Gas-fracturing experiments on finite-length boreholes indicate that the breakdown pressure is a strong function of fracturing fluid composition and state – converse to the principle of effective stress. Breakdown stress is shown to correlate with fluid exclusion or invasion into the borehole wall as a function of interfacial characteristics. Interfacial tension, in turn, is modulated by fluid state, as sub- or super-critical, and thus gas type and state influence the breakdown pressure. We explore linkages in the resulting fracture complexity that is indexed by breakdown pressure together with other factors related to the evolution of porosity in tight reservoirs.
Fractures with correlated and uncorrelated random aperture distributions were used to explore a fundamental scaling relationship between fracture stiffness and fluid flow in a fracture. Three computational methods were used: (1) a stratified percolation approach to generate pore-scale fracture void geometry for fractures, (2) a combined conjugate-gradient method and fast-multipole method for determining fracture deformation, and (3) a flow network model for simulating fluid flow, fluid velocity and fluid pressures within a fracture. Fracture specific stiffness captures the deformation of the fracture void geometry that includes both changes in contact area and aperture. The numerical flow-stiffness data, simulated at multiple length scales, collapsed to a single scaling function that displays different exponential regions above and below the transition into the critical regime. This hydro-mechanical scaling relationship provides the first step in determining fluid flow remotely through fractured rock because fracture specific stiffness affects seismic wave attenuation and velocity, which are routinely measured in the field.
Lüth, S. (GFZ German Research Centre for Geosciences) | Schmidt-Hattenberger, C. (GFZ German Research Centre for Geosciences) | Henninges, J. (GFZ German Research Centre for Geosciences) | Ivanova, A. (GFZ German Research Centre for Geosciences) | Gil, M. (GFZ German Research Centre for Geosciences) | Götz, J. (GFZ German Research Centre for Geosciences) | Bergmann, P. (GFZ German Research Centre for Geosciences) | Baumann, G. (GFZ German Research Centre for Geosciences)
Pilot sites storing small amounts of carbon dioxide in a variety of geological settings are an important component for the industrial and governmental stakeholders in order to gain operational experience in storage and in the monitoring at various scales. An important aspect is also to gain confidence in the ability of monitoring technologies to pay a significant contribution to the safe operation of larger scale demonstration and industry scale sites, especially in the perspective of the wider public.
The Ketzin Pilot Site for CO2 Storage has entered its post-closure phase after injection was terminated in the end of August 2013. For approximately 5 years, 67,271 metric tons of CO2 have been injected into a saline aquifer reservoir at 630 - 650 m depth. At the pilot site, various monitoring technologies were applied, including pulsed neutron gamma logging (PNG), electrical resistivity tomography (ERT) and borehole as well as surface seismic measurements. The integrated monitoring approach allowed to combine results of borehole logging, lab experiments and surface measurements in order to quantitatively estimate the proportion of stored CO2 in the reservoir which has actually been imaged in the geophysical anomalies.
During the injection phase of the pilot site, two repeat surveys of 3D time-lapse seismics were acquired. The repeat surveys were performed approximately one year and three years after injection started, respectively. Both surveys were able to detect a time-lapse amplitude anomaly characterized by strong lateral heterogeneity which can be interpreted as an indication of the reservoir's heterogeneity caused by the complex sedimentary history in a fluvial environment. The quantitative estimations indicate that approximately 90 – 95% of the CO2 injected were imaged by the surface seismic surveys, leaving the remaining proportion residing in a very thin layer (less than ~:5 m) undetected by the measurements.
Hashimoto, R. (Kyoto University) | Koyama, T. (Kansai University) | Kikumoto, M. (Yokohama National University) | Saito, T. (Yokohama National University) | Yamada, S. (Yokohama National University) | Araya, M. (Waseda University) | Iwasaki, Y. (Geo-Research Institute) | Ohnishi, Y. (Kansai University)
The Angkor ruin, a World Cultural Heritage in Cambodia, includes many masonry structures in dangers of collapse due to uneven settlement of the foundation ground. In order to select proper and effective methods for conservation, it is important to evaluate the stability of the structures considering the ground deformation. In the previous studies, as a numerical method which can simulate the discontinuous behaviors of the masonry blocks and the continuous deformation of the ground simultaneously, the coupled Numerical Manifold Method (NMM) and Discontinuous Deformation Analysis (DDA) was developed and extended to the elasto-plastic simulation code. In this paper, an application example of NMM-DDA to an actual problem in the Angkor ruin is provided. The stability analysis of the Bayon Central Tower, one of the most important masonry monuments in the Angkor was carried out. In the simulation, excavation of the foundation ground which is planned in restoration project was considered, and its influence on the behavior of the structure was discussed from the simulation results.
Fengming, L. I. (China Coal Research Institute) | Hongyan, L. I. (China Coal Research Institute) | Yujun, Zhang (State Key Laboratory of Coal Mining and Clean Utilization?China Coal Research Institute) | Fakui, X. U. (Tiandi Science & Technology Co.,Ltd)
The destruction of surface building caused by deformation and movement of strip mine slope is a difficult problem; the effective control on the surface deformation of the slope is of great scientific and practical value. To solve this problem, horizontal and vertical deformation observation methods were used to study the surface movement of strip mine slope of Fushun. The factors of surface deformation were deeply analyzed. According to the surface deformation features around the building, a new geological disaster prevention technology was proposed, called “Combination grouting”. Treatment effects of geological disasters were assessed through the water pressure test, coring, radar survey. The results show that the pore region was well filled and consolidated, surface subsidence was under control.
It is possible to obtain the information of the preferred orientation of microcracks in granite by the measurement of the P-wave velocity, because the value of P-wave velocity is directly related to the density of microcracks. Therefore, we can obtain the information of three-dimensional distribution of microcracks in granite by measuring P-wave velocity in various directions. Assuming that the three-dimensional distribution of microcracks in granite was caused by the stress release during coring, we can assess the stress state at the location of coring in the underground considering the relationship between three-dimensional distribution of P-wave velocity and microcracks. Differential Strain Curve Analysis (DSCA) is one of the methods to evaluate the stress state in the underground using rock samples based on the initiation of microcracks due to the stress release. Therefore, if the three-dimensional distribution of P-wave velocity is related to the orientation of microcrack distribution determined by DSCA, the stress state in the underground can be evaluated from the measurement of P-wave velocity.
Based on the above consideration, we try to investigate the relationship between the three-dimensional distribution of P-wave velocity and that of the crack parameter determined from DSCA by conducting both P-wave velocity measurements in various directions using a polyhedral specimen and DSCA using granite samples obtained from the same location. In addition, we consider the possibility to evaluate the stress state (directions and ratio of principal stress) in the underground from only P-wave velocity measurement.
From wave velocity measurement using a polyhedral specimen, we could obtain three-dimensional distribution of P-wave velocity. From DSCA, the values of crack parameters were obtained. A negative correlation between the P-wave velocity and the crack parameter obtained from DSCA was observed for granite. Additionally, by using the value of the P-wave velocity corresponding to the crack-free granite, we could evaluate the directions and ratio of principal stress in the underground. Consequently, it is possible to evaluate the directions and ratio of principal stress in the underground from P-wave velocity measurement in granite.